This invention relates generally to irrigation sprinkler devices of the type having a spray head defining one or more spray nozzles through which irrigation water is delivered in a selected pattern of distribution to surrounding vegetation. More particularly, this invention relates to an improved irrigation spray head which substantially resists spray pattern distortion such as atomization, misting or fogging in response to a relatively high water supply pressure.
Sprinkler spray heads are well known in the art, of the type adapted for mounting onto the upper end of a fixed or pop-up water supply riser and including one or more spray nozzles shaped to distribute irrigation water in a selected pattern to surrounding vegetation such as turf grass, shrubs and the like. In one common form, such spray heads are manufactured from relatively economical plastic to include an upper deflector plate assembled with a lower base ring for mounting onto a water supply riser, wherein the deflector plate and base ring cooperatively define one or more contoured spray nozzles through which water stream sprays are projected outwardly in a discrete pattern or patterns. A throttling screw is typically provided for variably adjusting the water flow rate and distance of throw. Such spray nozzle or nozzles may be configured to provide a quarter-circle, half-circle, three-fourths-circle, or full-circle spray pattern. Alternately, the spray nozzle or nozzles may be shaped to distribute irrigation water in one direction along a narrow strip, or in opposite directions along narrows strips. In some spray head designs, multiple flow ports in the spray head may be provided in an initially closed condition and adapted to be opened as desired to provide a customized spray pattern from a standard or generic spray head. Desirably, such multi-ported spray head is designed further to provide a substantially uniform precipitation rate over surrounding terrain, regardless of the specific pattern selected. For examples of sprinkler spray heads of this general type, see U.S. Pat. Nos. 4,189,099; 4,739,934; and 5,642,861.
These sprinkler spray heads provide satisfactory irrigation of a surrounding terrain area, with relatively uniform precipitation rates, when the water supplied to the spray head is at a pressure within a relatively narrow design pressure range, typically on the order of about 15-30 psi. However, when the water supply pressure varies from the design pressure range, inconsistencies and instabilities in the projected irrigation stream spray or sprays can and do occur. More specifically, as the water supply pressure increases, there is an increased tendency for the projected irrigation stream spray pattern to become distorted particularly due to atomization upon discharge passage through the spray nozzle. Significant atomization results in conversion of the projected water from a discrete stream spray of a known pattern shape to a mist or fog which can be haphazardly wind-blown or otherwise vaporize. As a result, the irrigation water does not reach the surrounding terrain in the desired precipitation pattern.
In a typical irrigation system, the water supply pressure can fluctuate significantly. For example, terrain elevation variations in a municipal water supply system can produce localized relatively high pressure regions wherein the water supply pressure can range from 40 psi to as high as 100 psi. Such relatively high water supply pressures unfortunately result in the operation of many sprinkler spray heads in many irrigation systems at water pressures greater than their intended design pressure range, creating significant spray pattern distortion to correspondingly reduce the effectiveness and efficiency of water delivery to vegetation.
The present invention is directed to an improved sprinkler spray head designed to provide consistent and predictable delivery of irrigation water to surrounding vegetation, substantially without misting or fogging in response to a relatively broad range of low to high water supply pressures.